The overall objective of the project is to gain some insight into the processes that were involved in the evolution of the bacterial genome. For the coming year we will be examining heteroduplexes formed between E. coli DNA and Salmonella typhimurium DNA in certain selected regions of the genome in order to understand better the molecular events that have occurred during divergence of these two genera. We will also be studying the process of fixation of large duplications. We will also continue with the construction of a genetic map for Serratia marcescens with the object of comparing the S. marcescens map with that of other enterobacteria in order to gain more understanding of evolutionary processes. Through these various experimental approaches, we hope to find out more about the various mechanisms that operated in the evolution of the bacterial geonme and the relationship of gene location and gene function in the bacterial cell of today.